To understand why behavioral residue is so essential to our work, consider one useful definition of personality: An individual’s unique pattern of thinking, feeling, and behaving that is consistent over time. If you alphabetize your book collection just once, that does not make you an organized person. If you try a new dish on a menu once, that does not suggest that broadmindedness is a part of your personality. For a behavior to be part of your personality, it should be something that you do repeatedly. To be truly organized, you must systematically shelve your books and keep putting them back in their proper places. Moreover, you should also organize your CDs and create folders for your e-mails and keep the corkscrew in the drawer assigned to corkscrews.
To be broadminded, you should try the unknown dish on the menu often, not just as a blip in your typically conservative eating repertoire. You should also prefer unconventional vacations to traditional ones, and you should enjoy risking an evening at an obscure dance performance rather than returning to see The Nutcracker year after year. Obviously, repeated behaviors leave more residue than the occasional aberration. Bedrooms and offices are often repositories of evidence for these repeated behaviors; that is, I believe, what makes them such good places to find out what people are like. The accumulated residue in a bedroom distills many more behaviors than could be recorded by an observer in an interview, or even after several meetings